Epidemiology

As Aspergillus species are ubiquitous, invasive aspergillosis (IA) is seen in all geographical regions, usually in immunocompromised patients, such as those with cancer and transplant recipients. The true incidence of aspergillosis, and all fungal diseases, is poorly understood; however, the global prevalence of chronic pulmonary aspergillosis is estimated to be 3,000,000 and the global annual incidence of IA is estimated to be over 300,000.[5]

The epidemiology of invasive fungal infections has changed worldwide in recent years due to an expanding at-risk population, with increasing numbers of solid organ and stem cell transplant recipients and newer immunosuppressive agents.[6][7] One study in the US found that the incidence of IA has remained stable over time, with a mean of 2.4 cases per 100,000 patients per year.[8] Another study found that the number of hospitalisations related to IA in the US increased by an average of 3% per year during 2000-2013.[6]

In one review of 595 IA cases, patients had the following underlying conditions: autologous stem cell transplantation (7%); allogeneic stem cell transplantation (25%); haematological malignancy (29%); solid organ transplantation (9%); AIDS (8%); solid organ tumour (4%); chronic granulomatous disease (2%); other pulmonary disease (9%); other underlying conditions (5%); none (2%).[9]

Based on one surveillance study in 2001-2002, the incidence of IA at 12 months after stem cell transplantation (SCT) was 0.5% in autologous recipients, 2.3% in allogeneic recipients with HLA-matched related donors, and 3.9% in those with unrelated donors.[10] The incidence has increased to 12% in some reported data.[11] Mortality at 1 year after SCT has improved but remains high, at 50% to 80%. Mortality is 80% to 90% when Aspergillus involves the brain or infection disseminates.[12]

In solid organ transplantation, the incidence at 12 months after transplant was 2.4%, 0.8%, 0.3%, and 0.1% in lung, heart, liver, and kidney transplants, respectively.[10] In a multi-centre prospective survey of haematological malignancies, patients with acute myelogenous leukaemia undergoing induction chemotherapy were at the highest risk for IA, with an incidence ranging from 8% to 10%.[13] Lesser incidence is seen in those with acute lymphocytic leukaemia and lymphoma.

Chronic pulmonary aspergillosis complicates other pulmonary diseases.[2] In one study, aspergillosis was detected in 4.9% to 6.3% of all treated pulmonary tuberculosis cases and 26% of cases with chest radiography cavitation.[14] According to another study, 11% of patients with pulmonary cavities secondary to tuberculosis have radiological evidence of aspergilloma.[15] In most cases of aspergilloma, the lesions remain stable without invasion of the pulmonary parenchyma or blood vessels.[15]

The prevalence of azole-resistant aspergillus is increasing in certain parts of the world, likely due to the use of antifungal medications in agriculture and pesticides.[16]

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